Newbie 2 tracker w/ recently acquired Otari MX-5050

[galyons]

I am new to the forum.  More importantly, I am new to prerecorded 2 track tapes.  I bought about 350 reel to reel tapes at an estate sale. Mostly classical with a few jazz, folk, opera and musicals.  In my buying frenzy, I did not notice that about 130 were 2-track! Most of the 2-tracks are late 50's RCA, Columbia and Mercury.  That's the good news!

The bad news is my Teac A4300 is a 4-track machine.  I recently brought my Teac back to life.  The heads are like new and functions to spec. But it, obviously, won?t play the 2 track tapes.  Additionally, I have a lot to learn about handling these classic tapes. I have been spoiled by the convenience of 4-track auto-reverse, but really excited about the better fidelity of the 2 tracks.

So, based on recommendations on the Tape Asylum, (Thanks Doc!),I picked up an Otari MX-5050 BIIHD. If I am interpreting the SN info correctly, it was built in 1981. It is in rack mount configuration, as it was in a radio station. Cosmetically it is pretty nice.  It is complete with all of the hubs. Heads show very little wear. So it appears to have been professionally used and maintained. It is not without issues, though.

The capstan slowed substantially after a few minutes of play. The lead 1000uf cap on the main board had leaked. Other than that cap, all the other caps appear to not have leaked. I de-gunked the cue pivot  and lever, which were stuck and now moves properly.

I am putting together my cap order. I plan to replace all of the main board 1000uf caps and the capstan drive board larger caps. What other function and reliability caps should I do?

I want to get everything running to spec before tweaking the I/O amp boards for sound. I will likely do a tubed outboard head amp.

Cheers,
Geary

[ironbut]

Hi Geary,

Welcome to the forum.

It sounds like you have some electrical knowledge and that will come in handy, but I often tell folks when they first jump into reel to reel repair that much of what has to be done is more mechanical in nature. Lubricating that pivot is a great place to start on Otari's.
I'd like to suggest that you check out the "Beginner's Guide" which is located above the General forum in a sticky. It was meant to pick up where owners manuals leave off and page two has a section with a shopping list. If you plan to do repairs to your machine, you really need to have some basic measuring tools to adjust things like tape tension and braking force. Those are both critical elements for taking good care of those early 2 track recordings. They can be rather delicate since most are on acetate and not too far away from being eligible for Medicare.
Regarding the replacement of caps, I suggest doing it in small steps once you have measurement tools to see how it effects things like tension.
If you've done any searching around here for Otari 5050 stuff, you'll notice that many issues are solved by cleaning and re-seating of the connectors on the circuit boards. If you're in there for something else, it's worth cleaning them.

Have fun. I really enjoy working on these machines.

[galyons]

Thanks Scott,
I spent  time on the sticky posts and will spend more. Very helpful. Thank you for your contributions.  I am pretty good with tube electronics, less so with solid state, but can read a schematic and wield a soldering iron.  I have built a DIY phono stage, restored several vintage amps, integrated amps and modded my "modern" amps and preamps. All of these projects were tube based. 

My mechanical abilities are more in the "brute force" than finesse category.  I'll look at the cost of the tension measuring tools. It may make more sense for me to have a tech handle that part.

I am really impressed with the build quality on the Otari.  I can definitely see the difference from my Teac A4300.  Plodding on...

Cheers,
Geary

[ironbut]

You can almost always find a couple of Tentelometers on eBay but there are many different versions. If you google Tetel you should be able to pull up info on the different models.
The prices range up to over $100 but I've never paid more than $50. The main thing you need to get is one that has the right probe length and the right measuring scale. I also like the ones with rolling probes and damping (easier to read). Mine is a variation of the T2-H20-1 with a 0-600 gram scale. You can get ones with a lower scale but they're super touchy and hard to read accurately. I also have one with a 0-150 gram scale but I've never found a way to keep the needle from jumping all over the place so I always use the other one (it could be broken).
When using these things, the key is to have a set of weights and calibrate it to the tension that you're looking for. Be aware that with ones without the rolling probes, the calibration will be different from side to side (it depends on which side the force is coming from,.. just like which side the calibration weight is hanging from). After you've calibrated the meter from one side, move the weight to the other so you can figure this compensation into your side to side measurements. Depending on the particular meter, this can be as much as 10 grams so do this carefully.

[galyons]

First I want to thank everyone who takes the time to post detailed info on dealing with the R2R decks.  The information here has assisted me in very quickly getting my "new to me" Otari functioning.  For every issue that I have, so far, discovered I found a resolution searching the posts here.

The bad cap was pretty obvious. I grabbed a cap from the local electronic supply house.  I have better caps coming and will replace the power and capstan drive large caps.  I had all the "round up the usual suspects" problems.  Cleaning and re-seating connectors, cleaning pots, cleaning the pitch pot, cleaning and lubing the capstan and edit pivot  points.  And now glorious music flowing, at least through my cheapy headphones.  I ordered some XLR plugs to build XLR to RCA interconnects, but they are yet to arrive.

Let the journey begin. 


Cheers,
Geary